The ability to reproducibly synthesize porous, rigid resins which are chemically stable to organic solvents over a wide pH range and which have a desired shape, size, porosity and surface area, has substantial commercial importance. The value is further enhanced if the resins can be modified to provide functionality suitable for ion exchange or other reactivity. One such technique is based upon use of inorganic particles having a desired size, surface area and porosity to extract the reactive components from a reaction mixture placed in contact with the inorganic particles, followed by polymerization of reactants within the pores of the inorganic particles and removal of the inorganic particles without destruction of the polymerizate. Theoretically, at least, the isolated polymerizate should mirror the size, surface area and porosity of the inorganic particles.
U.S. Pat. No. 4,263,268 to Knox and Gilbert describes a method of preparing porous carbon by depositing a polymerizable mixture in the pores of a porous inorganic template such as silica gel, polymerizing the mixture, pyrolyzing the resulting polymer, and dissolving the template material. This work is also reported in LC/GC 5 No. 2. (1987) 165.
U.S.S.R. Invention Description With Authors Certificate No. 208942, published Jan. 17, 1968, describes a method of preparing macroporous ion exchange resins by copolymerizing styrene with divinyl benzene in a porous matrix such as silica gel having a surface area of 200-300 m.sup.2 /g, an average pore diameter of 100-150 Angstroms, and a particle size of 1-2 mm. The resulting swollen particles are transferred to a saturated CaCl.sub.2 solution and the temperature raised to 70.degree. C. for 4-5 hours. The silica gel particles containing the copolymer are then combined with dichloroethane and heated for 30 minutes at 70.degree. C. The dichloroethane is washed out with ethyl ether and the resulting beads are allowed to stand 2-3 hours in an NaOH solution. The alkali is washed off the beads with distilled water and the beads are dried. The porosity of the resulting copolymer beads, determined by acetone, is 0.5 cm.sup.3 /g, and the specific area measured by BET is 150-200 m.sup.2 /g. The beads may be ion exchange functionalized by sulfonation in the usual manner.
The process of the U.S.S.R. publication appears to be a bulk copolymerization, the dichloroethane operating as an inert solvent and precipitant to dissolve the monomers but not the copolymer. The large proportion of monomers relative to the silica gel suggests that agglomeration is taking place. Moreover, the silica gel appears to be a conventional hydrophilic material and thus is incompatible with the hydrophobic monomers. Still further, the very large particle size of the silica gel indicates that the copolymer particles, once separated from the silica gel by treatment with the caustic, could not be used for high-performance chromatography. In any event, the pore volume of the silica gel is not given and therefore the efficiency of the copolymerization and the extent to which the copolymer mirrors the particle size and pore diameter of the silica gel cannot be determined.